Fatigue of bridges with a horizontal rotation axle under random wind load

The operating mechanisms of movable bridges are subjected to various types of fluctuating loads which may induce fatigue damage. Wind load acting on the bridge deck – when the bridge is open – is one of the important load types. A wind load model is proposed that can be used in the fatigue design verification. The model is based on wind statistics. It is presented as a Markov matrix that gives the probability of the combinations of mean wind loads and wind load fluctuations. The model will be implemented in the new version of the standard NEN 6786

The effect of climate change and natural variability on wind loading values

Since 2006, a number of countries developed reports on climate change following the IPCC 4th assessment reports. For the Netherlands, the Royal Netherlands Meteorological Institute (KNMI) presented four new climate scenarios. Typically, climate change is described in terms of average changes, but much of the social and economic costs associated with climate change in the built environment will result from shifts in the frequency and severity of extreme events. In this study, the consequences of the climate change scenarios on the design wind speeds used in building regulations are discussed. Based on the best actual available knowledge of climate change models, the effect of climate change implies a change of -0.8% to +2.3% in the hourly mean wind speed with return period of 50 years, which is the basis of current building codes. To confirm the outcomes, further development of climate change scenarios is needed with more focus on extreme events with large return periods and small time scales. Natural variability of wind speed appears to have a great effect on wind trends for extreme wind velocities, and when adapting values for extreme climatic effects in building codes, both climate change effects and effects of natural variability should be considered. The analysis as presented for extreme wind speeds can be applied to other domains, such as thermal and precipitation where extreme values of climatic conditions define building design, and can therefore serve as general framework to assess extreme events. -------------------------------------------------------------------------------

Climate change and its impact on structural safety

Extreme climatic events lead to loads on buildings and civil engineering works. Changes in climate will have an effect on the design loads. This paper presents an investigation into the relevance of the climate change scenarios with respect to the loads on buildings by wind, precipitation and temperature. Possible consequences to building codes are illustrated, and research questions are defined

Probabilistic traffic load model for short-span city bridges

In the coming years numerous existing traffic bridges in cities are subject to re-evaluation. In this paper a new probabilistic traffic load model for short-span bridges is proposed. As an example, site-specific weigh-in-motion data from Rotterdam, the Netherlands, is included in the model. The method proposed in this paper allows for a very efficient computation and at the same time takes into account the stochastics in axle loads and distances. For a simply supported 6 m single lane bridge the probabilistic load model provides a design load effect that is slightly lower than currently prescribed EN 1991-2 and the Dutch Guidelines for existing structures NEN 8700 and NEN 8701. This indicates that there is possible potential for a small reduction of the traffic load for short-span city bridges compared to the current standards. However, given the questionable quality of recorded measurements, a more extensive measurement campaign using WIM measurements is needed to get an adequate quantification of the traffic load parameters for city traffic conditions.Steel & Composite Structure

Simultaneous Vibration Suppression and Energy Harvesting in Wind Excited Tall Buildings Equipped with the Tuned Mass Damper Inerter (TMDI)

This paper investigates the potential of tuned mass dampers (TMDs) coupled with inerter devices in different tuned mass dampers inerter (TMDI) topologies to dissipate oscillations in tall buildings due to vortex shedding in the across wind direction while generating electric energy. The TMDI is first optimized for minimizing peak accelerations for serviceability purposes in a 74 storey benchmark steel building under different wind intensity levels. It is seen that TMDI stiffness and damping optimal parameters are robust to design/reference wind velocity and, therefore, to potential climate change effects, while achieving same level of performance using significantly smaller attached mass compared to the classical TMD. Then, a regenerative electromagnetic motor (EM) is added to the TMDI allowing for varying the TMDI damping property as well as transforming part of the dissipated kinetic energy to electricity. It is shown that by increasing TMDI damping above the optimal value for vibration suppression and/or by reducing the inerter property increases the available energy for harvesting at the expense of larger floor accelerations. Therefore, it is concluded that by relaxing serviceability limit state requirements associated with occupancy considerations renders possible an increase in energy generation in wind-excited tall building